The Bulletin Board is an object in Gather that you can select using the object picker. This is a good way to display information such as birthdays, holidays, game nights, meetings, lunchtimes, etc.
It's as simple as embedding a Google Document, Miro Board, or any other collaborative application into the Bulletin Board object. If you would like a more formal bulletin board that's not collaborative we recommend using a Google Doc that is not editable.
Here's an example Gather Bulletin Board for reference: